Announcement

Collapse
No announcement yet.

where to buy supermagnets in Canada

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • where to buy supermagnets in Canada

    The title says it all. I live in the Vancouver BC area, and I'd like to purchase neo magnets somewhat locally, but I'm having a hard time locating a supplier. I did find one place, but the minimum order was reediculous- maybe they just wanted to go for lunch and couldn't be bothered-

    Lee Valley sells disc magnets, but that's all. I'm looking for something rectangular, and would like to choose from a list of sizes and shapes. Nothing unusual, or so I thought. I believe I did once find a site in Ontario that sells these, but their selection was very limited as well.

    I can't read chinese, and though I love perusing their interpretation of the english language, I still haven't been able to locate a local supplier, whether their stock is from overseas or wherever. Can anybody clue me in here?
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    magnets

    Sorry, don't know but I found this 170262531678 on fleebay
    The difficult done right away. the impossible takes a little time.

    Comment


    • #3
      There are plenty of suppliers in the US that will ship to Canada. Any particular reason you don't want to order from them?

      While digging around on this subject I found out something about Neo magnets I didn't know. They are highly anisotropic in coefficient of linear and volumetric expansion with temperature.

      Thermal Expansion Coefficient (0 to 100°C) parallel to magnetization direction 5.2×10–6 /°C

      Thermal Expansion Coefficient (0 to 100°C) perpendicular to magnetization direction –0.8×10–6 /°C
      Free software for calculating bolt circles and similar: Click Here

      Comment


      • #4
        Princess Automotive

        Comment


        • #5
          digikey also has some, im not sure how the price compares though...

          Comment


          • #6
            I actually did not know until several years ago that magnets are formed into final shape and finished before being magnetized. It was also interesting to find out that some materials can only be magnetized in one direction, ie anisotropic. How that comes about in a material that's composed of a mixture of powders, I don't know. I could understand if they were pressed and sintered under the presence of a strong magnetic field, but otherwise how can there be a preferred direction of magnetization?

            I tried an experiment once with a neo disc- I heated it til it suddenly lost its magnetism, then tried to magnetize it sideways, ie across its diameter. It didn't work, but I got it to take magnetism in the normal direction, which was through the thickness.
            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

            Comment


            • #7
              My physics prof from last year recommended a place called Tridus International - he sang their praises. www.tridus.com

              Comment


              • #8
                I bought mine off ebay. Got 3/8's diameter by 1/2" and they are extremely handy. My daughter orderd some larger ones to decorate a public outdoor pavillion with wedding decorations and plans to re-ebay them when done. They work better then tape in this application. Do ebay, it's easy and you'll hve them in 2 or 3 days.
                - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                Thank you to our families of soldiers, many of whom have given so much more then the rest of us for the Freedom we enjoy.

                It is true, there is nothing free about freedom, don't be so quick to give it away.

                Comment


                • #9
                  I imagine that Darryl knows this but I'm sure not everyone does. Neo magnets are available in various grades that are identified with the letter N followed by a 2 digit value. Common cheap NEOs are usually N38 grade which is a low grade when dealing with NEO magnets. There are two main properties that change with the grade; maximum field strength and maximum operating temperature. The N38 grade magnets will start losing strength in boiling water while something like N52 NEOs are about twice as strong and can operate safely at several hundred degrees. The higher grades naturally cost more.
                  Free software for calculating bolt circles and similar: Click Here

                  Comment


                  • #10
                    My application is as motor magnets. It's entirely possible to have them overheat and lose it, especially in a compact powerhouse like model electric motors. Samarium has been specified for higher temperature use, but as Evan said there are grades of neo that will take more heat without failure. I wasn't aware that a higher operating temperature came along with the N52 grade, but I'll be looking for those for sure, mainly because my design will have a larger than normal air gap and will need to establish as much magnetic field strength as possible. What is it- inverse square law - double the gap reduces the strength by four times-

                    I have built several motors from scratch just for fun and education, and this will be another such project, except I intend to use it on the lathe. Most of my homemades use an existing armature, so they're not completely homemade, but a couple are. One is fairly large, draws an enormous amount of current, and doesn't produce much shaft power. The latest model will be patterned after this one, but will incorporate a proper laminated field structure, properly proportioned wire coils, magnet spacing, etc, and of course much much stronger magnets than the original test model. I'm hoping to be able to make this a sort of unversal diameter, so I can use the same size field structure for different power levels simply by changing the length of the lamination stack and the length of the magnets.

                    But- I don't have time for this project just yet, maybe it will be a winter thing.
                    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                    Comment


                    • #11
                      What is it- inverse square law - double the gap reduces the strength by four times-
                      Oh no, it's much worse than that. Magnetism follows inverse cube law. However, it is calculated from the center of mass assuming the field is approximately isotropic as it is from a large magnetized object like a planet. When you start dealing with shapes that don't approximate a sphere then the fields become unevenly concentrated and the power law breaks down just as they do with focused light sources. Pole pieces make it even more complex so there is no simple rule of thumb or mathematical relationship that can be applied. The strength of a magnetic field in such cases can only be calculated by means of numerical approaches such as Finite Element Analysis.
                      Free software for calculating bolt circles and similar: Click Here

                      Comment


                      • #12
                        Thanks Evan. That explanation adds a few pointers to my undrstanding of it all. My procedure is usually some ham fisted way to determine strength, like holding the magnet at the desired distance from the steel and gauging what the pull is.

                        From what you've said, I should be choosing thicker magnets, even though the area of the poles remain the same, so that the field lines penetrate further into my air gap and establish a higher field strength there, rather than bypassing around the magnet itself. The usable field strength cannot be gauged by measuring the pull required to remove a magnet from a steel surface.

                        A bit of a gray area for me has been with using pole pieces. It would seem to me that where the flux lines are being pushed on, as when passing a current through motor windings, it might be easier for the magnetic flux to bend out of the way to some extent through the pole piece, as opposed to having just the magnet as one border of the air gap. I have considered using pole pieces to bridge the gap between the flat magnet and the curve of the air gap, but I'm not sure what the effect would be. For a large radius of curvature and small width magnets, this wouldn't be an issue, but of course narrower magnets will also not project the magnetic field as far across an air gap.

                        Of course I can always use arc segment magnets, as long as the curvature is in the range where it works for me.
                        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                        Comment


                        • #13
                          Pole pieces concentrate the magnetic flux as it will follow the path of least resistance through the material with the highest permeability. This is a no free lunch proposition of course. While the magnetic field is concentrated by the pole pieces the extent is also reduced. Even thought the cube law is distorted it is still operating so reducing the volume of the field results in much faster drop off with distance. That BTW is why magnetic fields obey cube law. They are volumetric. In other words, if you use pole pieces then the separation to the other components becomes much more critical.

                          The other very important factor is what the pole pieces are made from. The magnetic permeability of iron alloys varies over a huge range. Ordinary mild steel may have a permeability of around 800 or so while electrical steel with high silicon content can be around 5,000. The glassy iron ribbon used in utility transformers now has a permeability in the hundreds of thousands.

                          So it really boils down to two things; using the right material for the pole pieces and maintaining high precision to minimize the air gaps. Obviously, using higher strength magnets can overcome such losses to a degree.
                          Free software for calculating bolt circles and similar: Click Here

                          Comment


                          • #14
                            sometimes reading Evans posts makes my brain hurt, and I get a sudden urge to go watch my "my name is Earl" DVD's.

                            Comment


                            • #15
                              That's another good point, Evan. I'm aware of differing magnetic capabilities of steels, but I didn't know the range of permeability was that much. Since I haven't found a source for glassy iron ribbon in any quantity that I could afford, I'm stuck with using electrical steel. My plan was to form the stator lamination structure from the cores of ballast transformers, or find a transformer with a wound core to be the donor. The latter is what I figure is most reasonable.

                              A key reason why one of my homemade motors is so inefficient is that I used steel wire to form the stator. Probably has a permeability of 2, and a hysterisis curve about as large as a farm I'd like to use a material which has a high saturation level, and I suppose this comes in part with high permeability. I'd like to learn more about this all, but when it comes to using a material to make my stator, I'll simply have to use what I can find and accept the results. I'll have to avoid using ordinary sheet steel, though ironically it's the easiest thing to find.
                              Last edited by darryl; 09-26-2008, 09:35 PM.
                              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                              Comment

                              Working...
                              X